Ultraviolet light can be used in heating, ventilation, and air conditioning (HVAC) systems to significantly reduce the amount of microbials in ductwork and air space, which helps to reduce possible health problems associated with inhaling microbials. Ultraviolet light is also beneficial in keeping HVAC coils free of mold, which increases system efficiency.
Ultraviolet (UV) light represents the frequency of light between 185 nanometers (nm) and 400 nm and is invisible to the naked eye. Within the UV spectrum lie three distinct bands of light: UV-A, UV-B, and UV-C. Longwave UV light (315 nm to 400 nm) or UV-A refers to what is commonly called “black light.” UV-B (280 nm to 315 nm) or midrange UV is the type of light that causes sunburn. Germicidal UV light (185 nm to 280 nm) or UV-C is effective in microbial control. Research has demonstrated that UV light between 254 nm and 265 nm is most efficient for microbial destruction. Germicidal lamps that produce the majority of their output in this range are the most effective in microbial control and destruction.
A typical HVAC system is used to maintain indoor air quality; however, the primary function of most HVAC systems is to control the temperature and humidity of the air. Many indoor air pollutants, such as volatile organic compounds (VOCs), cannot be removed by typical HVAC systems. Often, an air cleaning device may be added to HVAC systems to remove these VOCs. Photocatalytic air cleaning devices are a common technique for indoor air purification and deodorization. A photocatalytic air cleaning device in a HVAC system typically comprises an ultraviolet lamp that illuminates a photocatalytic filter to create free radicals that eliminate VOCs.